CVE-2018-19789: Disclosure of uploaded files full path

Affected versions

Symfony 2.7.0 to 2.7.49, 2.8.0 to 2.8.48, 3.0.0 to 3.4.19, 4.0.0 to 4.0.14,
4.1.0 to 4.1.8 and 4.2.0 versions of the Symfony Form component are affected by this
security issue.

The issue has been fixed in Symfony 2.7.50, 2.8.49, 3.4.20, 4.0.15, 4.1.9 and 4.2.1.

Note that no fixes are provided for Symfony 3.0, 3.1, 3.2 and 3.3 as they are not
maintained anymore.

Description

When using the scalar type hint string in a setter method (e.g. setName(string $name)) of a class that’s the data_class of a form, and when a file upload is submitted to the corresponding field instead of a normal text input, then UploadedFile::__toString() is called which will then return and disclose the path of the uploaded file. If combined with a local file inclusion issue in certain circumstances this could escalate it to a Remote Code Execution.

Resolution

File uploads are filtered out of form's data when the corresponding form type doesn't explicitly allow them.